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Plasma membrane H⁺ and K⁺ transporters are involved in the weak-acid preservative response of disparate food spoilage yeasts

Henrietta Rooney^1,

Marcus G. Jarman^1,

¹ Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
² Department of Agricultural Sciences, University of Tasmania, Hobart, Tasmania 7001, Australia

Correspondence
Julia M. Davies
jmd32{at}cam.ac.uk

The food spoilage yeasts Zygosaccharomyces bailii and Saccharomyces cerevisiae have been proposed to resist weak-acid preservative stress by different means; Z. bailii by limiting influx of preservative combined with its catabolism, S. cerevisiae by active extrusion of the preservative weak-acid anion and H⁺. Measurement of H⁺ extrusion by exponential-phase Z. bailii cells suggest that, in common with S. cerevisiae, this yeast uses a plasma membrane H⁺-ATPase to expel H⁺ when challenged by weak-acid preservative (benzoic acid). Simultaneous measurement of Z. bailii net H⁺ and K⁺ fluxes showed that net K⁺ influx accompanies net H⁺ efflux during acute benzoic acid stress. Such ionic coupling is known for S. cerevisiae in short-term preservative stress. Both yeasts significantly accumulated K⁺ on long-term exposure to benzoic acid. Analysis of S. cerevisiae K⁺ transporter mutants revealed that loss of the high affinity K⁺ uptake system Trk1 confers sensitivity to growth in preservative. The results suggest that cation accumulation is an important factor in adaptation to weak-acid preservatives by spoilage yeasts and that Z. bailii and S. cerevisiae share hitherto unsuspected adaptive responses at the level of plasma membrane ion transport.

Present address: Sainsbury Laboratory, John Innes Centre, Norwich NR4 7UH, UK.

Present address: Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2XY, UK.